Method and apparatus for transmitting data in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system. In detail, the present invention is a method for transmitting data to a base station (BS) by a user equipment (UE) includes: receiving information on a contention-based Physical Uplink Shared Channel (PUSCH) zone including a plurality of contention-based PUSCH resource blocks from the base station (BS); allocating at least one contention-based PUSCH resource block for transmission of the data based on the information on contention-based PUSCH zone; and transmitting the data to the base station (BS).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2015/001570, filed on Feb. 16, 2015,which claims the benefit of U.S. Provisional Application Nos.61/940,475, filed on Feb. 16, 2014 and 61/944,038, filed Feb. 24, 2014,the contents of which are all hereby incorporated by reference herein intheir entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for performing a random access procedurein a carrier aggregation (CA)-based wireless communication system and anapparatus for the same.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services including voice and dataservices. In general, a wireless communication system is a multipleaccess system that supports communication among multiple users bysharing available system resources (e.g. bandwidth, transmit power,etc.) among the multiple users. The multiple access system may adopt amultiple access scheme such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), or singlecarrier frequency division multiple access (SC-FDMA).

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina method for efficiently performing transmission of data in a wirelesscommunication system and an apparatus for the same. Another object ofthe present invention is to provide a method for efficiently performingrandom access procedure. Another object of the present invention is toprovide a method and apparatus for efficiently performing a buffer statereport.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Technical Solution

The object of the present invention can be achieved by providing amethod for transmitting data to a base station (BS) by a user equipment(UE) including: receiving information on a contention-based PhysicalUplink Shared Channel (PUSCH) zone including a plurality ofcontention-based PUSCH resource blocks from the base station (BS);allocating at least one contention-based PUSCH resource block fortransmission of the data based on the information on contention-basedPUSCH zone; and transmitting the data to the base station (BS), whereinthe at least one contention-based PUSCH resource block is determinedbased on a preamble sequence.

The at least one contention-based PUSCH resource block may be determinedby the following equation,Contention-based PUSCH resource block=(Preamble Sequence)modN  [Equation]

where N is a modulo operation, and N is the number of contention-basedPUSCH resource blocks contained in the contention-based PUSCH zone.

The method may further include: receiving a preamble sequence of acontiguous user equipment (UE) from the contiguous UE, wherein the atleast one contention-based PUSCH block is determined based on thepreamble sequence of the contiguous UE. The at least onecontention-based PUSCH block may be sequentially selected with respectto the preamble sequence. The preamble sequence may be arbitrarilyselected by the UE, or is allocated from the base station (BS). Thepreamble sequence may include a preamble sequence for random accessprocedure. The transmitting the data to the base station (BS) mayinclude: transmitting a preamble for the random access procedure.

In accordance with another aspect of the present invention, a method fortransmitting data to a base station (BS) by a user equipment (UE)includes: receiving information on a contention-based Physical UplinkShared Channel (PUSCH) zone including a plurality of contention-basedPUSCH resource blocks from the base station (BS); allocating at leastone contention-based PUSCH resource block for transmission of the databased on the information on contention-based PUSCH zone; andtransmitting the data to the base station (BS), wherein the at least onecontention-based PUSCH resource block is determined based on a UEidentifier (ID).

The at least one contention-based PUSCH resource block may be determinedby the following equation,(Number of UE-selected CPRB block)=(UE ID)mod N  [Equation]

where mod is a modulo operation, and N is the number of contention-basedPUSCH resource blocks contained in the contention-based PUSCH zone.

In accordance with another aspect of the present invention, a method fortransmitting data to a base station (BS) by a user equipment (UE)includes: receiving information on a contention-based Physical UplinkShared Channel (PUSCH) zone including a plurality of contention-basedPUSCH resource blocks from the base station (BS); allocating at leastone contention-based PUSCH resource block for transmission of the databased on the information on contention-based PUSCH zone; andtransmitting the data to the base station (BS), wherein the at least onecontention-based PUSCH resource block is arbitrarily determined.

The at least one contention-based PUSCH resource block may be selectedfrom among the contention-based PUSCH resource blocks contained in thecontention-based PUSCH zone after lapse of a predetermined back-off timefrom an expiration time of a timer needed for data transmission.

In accordance with another aspect of the present invention, a method fortransmitting data by a base station (BS) includes: transmittinginformation on a contention-based Physical Uplink Shared Channel (PUSCH)zone including a plurality of contention-based PUSCH resource blocks toa first user equipment (UE); and receiving the data from the first UE,wherein the data is allocated to at least one contention-based PUSCHresource block based on the information on contention-based PUSCH zone,and is then transmitted, wherein the at least one contention-based PUSCHresource block is determined based on a preamble sequence.

The at least one contention-based PUSCH resource block may be determinedby the following equation,Contention-based PUSCH resource block=(Preamble Sequence)modN  [Equation]

where N is a modulo operation, and N is the number of contention-basedPUSCH resource blocks contained in the contention-based PUSCH zone.

The method may further include: allocating a preamble sequence to eachof the first UE and a second UE, wherein the preamble sequence isallocated in such a manner that different contention-based PUSCHresource blocks are determined based on the equation.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

According to the present invention, it is possible to efficientlytransmit data in a wireless communication system. In addition, it ispossible to efficiently perform random access and transmit/receivecontrol information (e.g. acknowledgement information) involved in therandom access procedure.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same;

FIG. 2 is a diagram for structures of control and user planes of radiointerface protocol between a 3GPP radio access network standard-baseduser equipment and E-UTRAN;

FIG. 3 illustrates a radio frame structure;

FIG. 4 illustrates a resource grid of a downlink slot;

FIG. 5 illustrates a downlink subframe structure;

FIG. 6 illustrates an uplink subframe structure;

FIG. 7 illustrate random access procedures;

FIG. 8 is a conceptual diagram illustrating a latency time during arandom access procedure according to an embodiment of the presentinvention;

FIGS. 9 and 10 are conceptual diagrams illustrating a contention-basedPUSCH zone and a contention PUSCH resource block;

FIG. 11 is a conceptual diagram illustrating a method for configuring aCP zone;

FIG. 12 is a flowchart illustrating a random access procedure when theCP zone is not configured according to an embodiment;

FIG. 13 is a flowchart illustrating a random access procedure when theCP zone is configured according to another embodiment;

FIG. 14 is a flowchart illustrating the effect achieved when the CP zonefor the random access procedure is configured;

FIG. 15 is a conceptual diagram illustrating a specific situation inwhich two UEs perform the random access procedure when the CP zone isconfigured;

FIG. 16 is a conceptual diagram illustrating a method for occupyingresources according to an embodiment of the present invention;

FIG. 17 is a conceptual diagram illustrating a method for occupyingresources according to another embodiment of the present invention;

FIG. 18 is a flowchart illustrating a random access procedure performedbased on the resource occupying method shown in FIG. 17;

FIG. 19 is a flowchart illustrating a resource occupying methodaccording another embodiment of the present invention; and

FIG. 20 is a block diagram for an example of a communication deviceaccording to one embodiment of the present invention.

BEST MODE

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with an MS may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with the term ‘fixedstation’, ‘Node B’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’,etc. The term ‘UE’ may be replaced with the term ‘Mobile Station (MS)’,‘Mobile Subscriber Station (MSS)’, ‘mobile terminal’, etc.

In the following description, specific terminologies used forembodiments of the present invention are provided to help theunderstanding of the present invention. And, the use of the specificterminology may be modified into another form within the scope of thetechnical idea of the present invention.

In some instances, known structures and devices are omitted or shown inblock diagram form, focusing on important features of the structures anddevices, so as not to obscure the concept of the present invention. Thesame reference numbers will be used throughout this specification torefer to the same or like parts.

Embodiments of the present invention may be supported by the standarddocuments disclosed in at least one of wireless access systems includingIEEE (Institute of Electrical and Electronics Engineers) 802.16m system,3GPP system, 3GPP LTE system, 3GPP LTE-A (LTE-Advanced) system and 3GPP2system. In particular, the steps or parts, which are not explained toclearly reveal the technical idea of the present invention, in theembodiments of the present invention may be supported by the abovedocuments. Moreover, all terminologies disclosed in this document may besupported by the above standard documents.

Embodiments of the present invention are applicable to a variety ofwireless access technologies such as code division multiple access(CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), and single carrier frequency division multiple access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, and EvolvedUTRA (E-UTRA). 3^(rd) Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) evolves from 3GPP LTE. WiMAX is can be explained by IEEE 802.16estandard (WirelessMAN-OFDMA Reference System) and advanced IEEE 802.16mstandard (WirelessMAN-OFDMA Advanced system). Although the embodiment ofthe present invention will be described based on the LTE system and theLTE-A system in this specification, the LTE system and the LTE-A systemare only exemplary, and the embodiment of the present invention may beapplied to all communication systems corresponding to the aforementioneddefinition. Also, although the embodiment of the present invention willbe described based on an FDD mode in this specification, the FDD mode isonly exemplary, and the embodiment of the present invention may easilybe applied to an H-FDD mode or a TDD mode.

In a wireless communication system, a UE receives information from a BSon downlink (DL) and transmits information to the BS on uplink (UL).Information transmitted/received between the BS and the UE includes dataand various types of control information and various physical channelsare present according to type/purpose of informationtransmitted/received between the BS and the UE.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

When powered on or when a UE initially enters a cell, the UE performsinitial cell search involving synchronization with a BS in step S101.For initial cell search, the UE synchronizes with the BS and acquireinformation such as a cell Identifier (ID) by receiving a primarysynchronization channel (P-SCH) and a secondary synchronization channel(S-SCH) from the BS. Then the UE may receive broadcast information fromthe cell on a physical broadcast channel (PBCH). In the mean time, theUE may check a downlink channel status by receiving a downlink referencesignal (DL RS) during initial cell search.

After initial cell search, the UE may acquire more specific systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

The UE may perform a random access procedure to access the BS in stepsS103 to S106. For random access, the UE may transmit a preamble to theBS on a physical random access channel (PRACH) (S103) and receive aresponse message for preamble on a PDCCH and a PDSCH corresponding tothe PDCCH (S104). In the case of contention-based random access, the UEmay perform a contention resolution procedure by further transmittingthe PRACH (S105) and receiving a PDCCH and a PDSCH corresponding to thePDCCH (S106).

After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108), as a general downlink/uplink signaltransmission procedure. Control information transmitted from the UE tothe BS is referred to as uplink control information (UCI). The UCIincludes hybrid automatic repeat and requestacknowledgement/negative-acknowledgement (HARQ-ACK/NACK), schedulingrequest (SR), channel state information (CSI), etc. The CSI includes achannel quality indicator (CQI), a precoding matrix indicator (PMI), arank indicator (RI), etc. While the UCI is transmitted on a PUCCH ingeneral, the UCI may be transmitted on a PUSCH when control informationand traffic data need to be simultaneously transmitted. In addition, theUCI may be aperiodically transmitted through a PUSCH according torequest/command of a network.

FIG. 2 is a diagram for structures of control and user planes of radiointerface protocol between a 3GPP radio access network standard-baseduser equipment and E-UTRAN. The control plane means a path on whichcontrol messages used by a user equipment. (UE) and a network to managea call are transmitted. The user plane means a path on which such a datagenerated in an application layer as audio data, internet packet data,and the like are transmitted.

A physical layer, which is a 1st layer, provides higher layers with aninformation transfer service using a physical channel. The physicallayer is connected to a medium access control layer situated above via atransport channel (trans antenna port channel). Data moves between themedium access control layer and the physical layer on the transportchannel. Data moves between a physical layer of a transmitting side anda physical layer of a receiving side on the physical channel. Thephysical channel utilizes time and frequency as radio resources.Specifically, the physical layer is modulated by OFDMA (orthogonalfrequency division multiple access) scheme in DL and the physical layeris modulated by SC-FDMA (single carrier frequency division multipleaccess) scheme in UL.

Medium access control (hereinafter abbreviated MAC) layer of a 2nd layerprovides a service to a radio link control (hereinafter abbreviated RLC)layer, which is a higher layer, on a logical channel. The RLC layer ofthe 2nd layer supports a reliable data transmission. The function of theRLC layer may be implemented by a function block within the MAC. PDCP(packet data convergence protocol) layer of the 2nd layer performs aheader compression function to reduce unnecessary control information,thereby efficiently transmitting such IP packets as IPv4 packets andIPv6 packets in a narrow band of a radio interface.

Radio resource control (hereinafter abbreviated RRC) layer situated inthe lowest location of a 3rd layer is defined on a control plane only.The RRC layer is responsible for control of logical channels, transportchannels and physical channels in association with a configuration, are-configuration and a release of radio bearers (hereinafter abbreviatedRBs). The RB indicates a service provided by the 2nd layer for a datadelivery between the user equipment and the network. To this end, theRRC layer of the user equipment and the RRC layer of the networkexchange a RRC message with each other.

A single cell consisting of an eNode B (eNB) is set to one of 1.25 MHz,2.5 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz of bandwidths and thenprovides a downlink or uplink transmission service to a plurality ofuser equipments. Different cells can be configured to providecorresponding bandwidths, respectively.

DL transport channels for transmitting data from a network to a userequipment include a BCH (broadcast channel) for transmitting a systeminformation, a PCH (paging channel) for transmitting a paging message, adownlink SCH (shared channel) for transmitting a user traffic or acontrol message and the like. DL multicast/broadcast service traffic ora control message may be transmitted on the DL SCH or a separate DL MCH(multicast channel).

Meanwhile, UL transport channels for transmitting data from a userequipment to a network include a RACH (random access channel) fortransmitting an initial control message, an uplink SCH (shared channel)for transmitting a user traffic or a control message. A logical channel,which is situated above a transport channel and mapped to the transportchannel, includes a BCCH (broadcast channel), a PCCH (paging controlchannel), a CCCH (common control channel), a MCCH (multicast controlchannel), a MTCH (multicast traffic channel) and the like.

FIG. 3 illustrates a radio frame structure. Uplink/downlink data packettransmission is performed on a subframe-by-subframe basis. A subframe isdefined as a predetermined time interval including a plurality ofsymbols. 3GPP LTE supports a type-1 radio frame structure applicable tofrequency division duplex (FDD) and a type-2 radio frame structureapplicable to time division duplex (TDD).

FIG. 3(a) illustrates a type-1 radio frame structure. A downlinksubframe includes 10 subframes each of which includes 2 slots in thetime domain. A time for transmitting a subframe is defined as atransmission time interval (TTI). For example, each subframe has aduration of 1 ms and each slot has a duration of 0.5 ms. A slot includesa plurality of OFDM symbols in the time domain and includes a pluralityof resource blocks (RBs) in the frequency domain. Since downlink usesOFDM in 3GPP LTE, an OFDM symbol represents a symbol period. The OFDMsymbol may be called an SC-FDMA symbol or symbol period. An RB as aresource allocation unit may include a plurality of consecutivesubcarriers in one slot.

The number of OFDM symbols included in one slot may depend on cyclicprefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When achannel state is unstable, such as a case in which a UE moves at a highspeed, the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 3(b) illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 5 normalsubframes DwPTS (Downlink Pilot Time Slot), GP (Guard Period), and UpPTS(Uplink Pilot TimeSlot). A subframe is composed of 2 slots. DwPTS isused for initial cell search, synchronization or channel estimation in aUE and UpPTS is used for channel estimation in a BS and uplinktransmission synchronization in a UE. The GP eliminates UL interferencecaused by multi-path delay of a DL signal between a UL and a DL.Meanwhile, one subframe composed of 2 slots regardless of a type ofradio frame.

The radio frame structure is merely exemplary and the number ofsubframes included in the radio frame, the number of slots included in asubframe, and the number of symbols included in a slot can be vary.

FIG. 4 illustrates a resource grid of a downlink slot.

Referring to FIG. 4, a downlink slot includes a plurality of OFDMsymbols in the time domain. While one downlink slot may include 7 OFDMsymbols and one resource block (RB) may include 12 subcarriers in thefrequency domain in the figure, the present invention is not limitedthereto. Each element on the resource grid is referred to as a resourceelement (RE). One RB includes 12×7 REs. The number NRB of RBs includedin the downlink slot depends on a downlink transmit bandwidth. Thestructure of an uplink slot may be same as that of the downlink slot.

FIG. 5 illustrates a downlink subframe structure.

Referring to FIG. 5, a maximum of three (four) OFDM symbols located in afront portion of a first slot within a subframe correspond to a controlregion to which a control channel is allocated. The remaining OFDMsymbols correspond to a data region to which a physical downlink sharedchancel (PDSCH) is allocated. A basic resource unit of the data regionis an RB. Examples of downlink control channels used in LTE include aphysical control format indicator channel (PCFICH), a physical downlinkcontrol channel (PDCCH), a physical hybrid ARQ indicator channel(PHICH), etc. The PCFICH is transmitted at a first OFDM symbol of asubframe and carries information regarding the number of OFDM symbolsused for transmission of control channels within the subframe. The PHICHis a response of uplink transmission and carries an HARQ acknowledgment(ACK)/negative-acknowledgment (NACK) signal. Control informationtransmitted through the PDCCH is referred to as downlink controlinformation (DCI). The DCI includes uplink or downlink schedulinginformation or an uplink transmit power control command for an arbitraryUE group.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). Formats 0, 3, 3A and 4 for uplinkand formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink are definedas DCI formats. Information field type, the number of informationfields, the number of bits of each information field, etc. depend on DICformat. For example, the DCI formats selectively include informationsuch as hopping flag, RB assignment, MCS (Modulation Coding Scheme), RV(Redundancy Version), NDI (New Data Indicator), TPC (Transmit PowerControl), HARQ process number, PMI (Precoding Matrix Indicator)confirmation as necessary. Accordingly, the size of control informationmatched to a DCI format depends on the DCI format. A arbitrary DCIformat may be used to transmit two or more types of control information.For example, DIC formats 0/1A is used to carry DCI format 0 or DICformat 1, which are discriminated from each other using a flag field.

A PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE is alogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

FIG. 6 illustrates an uplink subframe structure.

Referring to FIG. 6, an uplink subframe includes a plurality of (e.g. 2)slots. A slot may include different numbers of SC-FDMA symbols accordingto CP lengths. For example, a slot may include 7 SC-FDMA symbols in anormal CP case. The uplink subframe is divided into a control region anda data region in the frequency domain. The data region is allocated witha PUSCH and used to carry a data signal such as audio data. The controlregion is allocated a PUCCH and used to carry control information. ThePUCCH includes an RB pair (e.g. m=0, 1, 2, 3) located at both ends ofthe data region in the frequency domain and hopped in a slot boundary.Control information includes HARQ ACK/NACK, CQI, PMI, RI, etc.

A description will be given of a random access procedure. The randomaccess procedure is referred to as a random access channel (RACH)procedure. The random access procedure is used for initial access,uplink synchronization control, resource assignment, handover,reestablishing radio link after radio link failure, estimating oflocation, etc. The random access procedure is classified intocontention-based procedure and a dedicated (i.e. non-contention-based)procedure. The contention-based random access procedure includes initialaccess and is normally used and the dedicated random access procedure islimited to handover, reconfiguring uplink synchronization for estimatingof location, when downlink data is arrived, etc. In the contention-basedrandom access procedure, a UE randomly selects an RACH preamblesequence. Accordingly, a plurality of UE can simultaneously transmit thesame RACH preamble sequence, which requires a contention resolutionprocedure. In the dedicated random access procedure, the UE uses an RACHpreamble sequence uniquely allocated thereto by the BS. Accordingly, theUE can perform the random access procedure without collision with otherUEs.

FIGS. 7(a) and 7(b) illustrate random access procedures. FIG. 7(a) showsa contention-based random access procedure and FIG. 7(b) shows adedicated random access procedure.

Referring to FIG. 7(a), the contention-based random access procedureincludes the following four steps. Messages transmitted in steps 1 to 4may be respectively referred to as messages (Msg) 1 to 4.

-   -   Step 1: UE transmits RACH preamble via PRACH    -   Step 2: UE receives Random access response (RAR) from eNB via        DL-SCH    -   Step 3: UE transmits Layer2/Layer3 message to eNB via UL-SCH    -   Step 4: UE receives Contention resolution message from eNB via        DL-SCH

Referring to FIG. 7(b), the dedicated random access procedure includesthe following three steps. Messages transmitted in steps 0, 1 and 2 maybe respectively referred to as messages (Msg) 0, 1 and 2. Uplinktransmission (i.e. step 3) corresponding to RAR may be performed as partof the random access procedure, which is not shown in the figure. Thededicated random access procedure may be triggered using a PDCCH(referred to as PDCCH order hereinafter) used for the BS to order RACHpreamble transmission.

-   -   Step 0: eNB allocates RACH preamble to UE through dedicated        signaling    -   Step 1: UE transmits RACH preamble to eNB via PRACH    -   Step 2: UE receives Random access response (RAR) via DL-SCH

After transmission of the RACH preamble, the UE attempts to receive aRAR within a predetermined time window. Specifically, the UE attempts todetect a PDCCH (referred to as an RA-RNTI PDCCH hereinafter) having aRA-RNTI (e.g. CRC in the PDCCH is masked with RA-RNTI) within the timewindow. The UE checks whether a PDSCH corresponding to the RA-RNTI PDCCHincludes a RAR therefor when RA-RNTI PDCCH is detected. The RAR includestiming alignment (TA) information representing timing offset informationfor UL synchronization, UL resource allocation information (UL grantinformation), a temporary UE identifier (e.g. temporary Cell-RNTI(TC-RNTI)), etc. The UE may perform UL transmission (e.g. message 3)according to resource allocation information and a TA value included inthe RAR. HARQ is applied to UL transmission corresponding to the RAR.Accordingly, the UE may receive acknowledgement information (e.g. PHICH)corresponding to message 3 after transmission of message 3. For example,Message 3 may include the RRC connection request message for initialaccess. The UE having transmitted Message 3 may receive a contentionresolution message (Message 4) from the BS or eNB. In this step, the UEmay resolve the contention caused by a plurality of UEs attempting toaccess the system using the same random access resources. If the UEsuccessfully receives Message 4, TC-RNTI is promoted to C-RNTI. Ifidentity transmitted from step 3 is different from identity receivedfrom step 4, the UE may determine a failure in random access resources,so that the UE returns to step 1. In addition, after transmission ofmessages in step 3, if messages of step 4 are not received within aspecific time, the UE may declare the occurrence of a random accessfailure, and may return to step 1. However, in the case of the dedicatedrandom access process, the contention resolution is no longer required,such that only two steps are carried out.

FIG. 8 is a conceptual diagram illustrating a latency time during arandom access procedure according to an embodiment of the presentinvention.

Referring to FIG. 8, in step 3 indicating the contention-based randomaccess procedure, the UE may transmit the RRC/NAS (non-access stratum)request message for transmitting its own information to the network. TheUE must receive UL resources for the RRC/NAS request message, so thatthe contention-based random access procedure is carried out while beingclassified into four steps.

The following Table 1 shows the result for measuring the latency timewhen the above four-stage random access procedure for initial networkaccess is carried out. The latency time of the four-stage random accessprocedure will be analyzed using the following Table 1.

TABLE 1 Com- Time ponent 

Description 

(ms) 

1 

Average delay due to RACH scheduling 0.5 

period (1 ms RACH cycle) 

2 

RACH Preamble 

1 

3-4 

Preamble detection and transmission of 3 

RA response (Time between the end RACH transmission and UE's receptionof scheduling grant and timing adjustment) 

5 

UE Processing Delay (decoding of scheduling 5 

grant, timing alignment and C-RNTI assignment + L1 encoding of RRCConnection Request) 

6 

Transmission of RRC and NAS Request 

1 

7 

Processing delay in eNB (L2 and RRC) 

4 

8 

Transmission of RRC Connection 1 

Set-up (and UL grant) 

Referring to Table 1, a total latency time reaching Component 8 of theRRC connection configuration message corresponding to the 8^(th) step ofFIG. 8(a) is about 15.5 [ms].

Referring to FIG. 8(b), the UE configured to perform handover during theconventional noncontention-based random access procedure transmits theRACH preamble, receives the random access response from the eNB, andtransmits the RRC connection reconfiguration complete message to theeNB. In this case, a detailed description of the latency time isdescribed in the standard document as shown in Table 2.

TABLE 2 Com- Time ponent 

Description 

[ms] 

1 

Ratio synchronisation to the target cell 

1 

2 

Average delay due to RACH scheduling 0.5 

period (1 ms periodicity) 

3 

RACH Preamble 

1 

4-5 

Preamble detection and transmission of 5 

RA response (Time between the end RACH transmission and UE'S receptionof scheduling grant and timing adjustment) 

6 

Decoding of scheduling grant and 2 

timing alignment 

7 

Transmission of DL Data 

1 

Total delay 

10.5 

Referring to Table 2, a total latency time to transmission (Component 7)of DL data for use in the 7^(th) step of FIG. 8 is about 10.5 [ms].

As described above, the LTE system uses the data transmission/reception(Tx/Rx) method based on eNB scheduling so as to maximize availability ofresources. In more detail, when the UE transmits data to the eNB, the UEfirstly requests the eNB from UL resource allocation, and can transmitdata using UL resources allocated from the eNB. Therefore, according tothe conventional UL data transmission, the latency time caused byresources allocated from the eNB may increase.

A method for defining the contention-based PUSCH zone to minimize thelatency time in a UE control region will hereinafter be described. As aresult, if the UE located in the cell in which the contention-basedPUSCH zone is configured transmits UL data requesting a short latencytime (i.e., a low latency), the UE can transmit data using thecorresponding zone without scheduling of the eNB. Meanwhile, thecontention-based PUSCH zone proposed by the present invention may belimited only to UL data (e.g., the RRC/NAS request message for randomaccess or the BSR message for BSR) transmitted within a specificprocedure. The contention-based PUSCH zone (hereinafter referred to as‘CP zone’) and the contention PUSCH resource block (hereinafter referredto as ‘CPRB’) will hereinafter be described.

Definition of CP Zone and CPRB

FIGS. 9 and 10 are conceptual diagrams illustrating a contention-basedPUSCH zone and a contention PUSCH resource block.

Referring to FIG. 9, the CP zone may be allocated to a specific resourceregion within PUSCH for UL data transmission. For example, the CP zonemay be allocated to one subframe or contiguous subframes. In addition, aresource region capable of being occupied by one arbitrary UE within aspecific resource region is defined as a contention-based PSUCH resourceblock (CPRB). That is, N CPRBs may be defined in one CP zone.

Referring to FIG. 10, the UE may attempt to occupy the CPRB at aspecific time. In this case, a specific region in which an arbitrary UEcan attempt to occupy the CPRB at a specific time is referred to as a ULcontention group. The UL contention group may include M CP zones. One CPzone may include N CPRBs capable of being occupied by the UE. In thiscase, (N×M) may indicate the number of CPRBs (hereinafter referred to ascandidate CPRBs) through which one UE can be selected in thecorresponding contention group at a specific time.

If a contention group is configured in two subframes and one CP zone isdefined on a subframe basis, (2×N) candidate CPRBs can be occupied bythe UE of the corresponding contention group. That is, the UE may have2N candidate CPRBs, and may transmit data through at least one CPRB fromamong the 2N candidate CPRBs without receiving the UL grant. Forexample, if 2 zones each having 4 CPRBs are contained in one contentiongroup, the UE may have (N×M) candidate CPRBs (where N×M=8). Meanwhile,the UE can transmit data through one CPRB from among 2N candidate CPRBswithout receiving the UL grant, and has to separately acquireinformation needed for transmission of data to be transmitted throughthe legacy UL grant.

A method for configuring the CP zone for the random access procedurewill hereinafter be described in detail.

Method for Transmitting Information Related to CP Zone

In accordance with the present invention, a specific cell may transmitinformation regarding the CP zone to the UE. It is necessary for thespecific cell to inform the UE that the corresponding cell is a cellhaving the CP zone. In addition, in order for the UE to transmit datawithout receiving the UL grant, it is necessary for the eNB to informthe UE of information needed for transmission of the above dataaccording to another method. Information regarding the CP zone mayinclude information indicating that the above specific cell is a cellhaving the CP zone or other information needed for data transmissionusing the CP zone. Four methods for transmitting information on the CPzone will hereinafter be described in detail. The above information isone of cell common information pieces, so that this can be transmittedas one of the system information. In more detail, the CP zoneinformation may be used as a broadcasting message (e.g., systeminformation or Master Information Block (MIB), etc.), and may betransmitted from the BS or eNB. If necessary, the CP zone message isdefined as a unicast message for a specific UE, and may then betransmitted. Preferably, the specific cell may be a small cell.

First Scheme: The CP zone information may be transmitted through the MIBtransmitting essential physical layer information. In this case, the CPzone information may be transmitted through a field added to the MIB.

Second Scheme: The CP zone information may be transmitted through aconventional system information block (SIB). In this case, theconventional system information block may be referred to as SIB-x. TheCP zone information may be transmitted through SIB-x (e.g., SIB-1,SIB-2, etc.) as necessary. Preferably, if the CP zone is configured forrandom access, the CP zone information may be requisite for initialnetwork access, so that this CP zone information may be transmittedthrough SIB-2. That is, if the CP zone is configured for the randomaccess procedure, the CP zone information may be contained in the legacySIB2 so that it may be transmitted from the eNB to the UE. Therefore,the UE having received the above message may previously recognize thatthe UE can be connected to the cell by transmitting the RRC connectionrequest message through the CP zone.

Third Scheme: Information regarding the CP zone may be transmittedthrough a new SIB. In this case, this new SIB is referred to as SIB-y.For example, if the CP zone is configured for the procedure locatedafter the network access, the CP zone information may be transmittedthrough a newly defined SIB. In this case, the eNB may previously informthe UE that a specific cell connected to the UE is a cell that has toreceive the new SIB. This information message may be transmitted throughMIB or SIB. Preferably, the SIB may be SIB1 or SIB2.

Fourth Scheme: The above-mentioned information may be transmittedthrough a new control message according to the unicast scheme. If the UEis connected to the corresponding cell, the corresponding zoneinformation may be received only by the UE that desires to use the CPzone.

Transmission of the CP zone information is not limited to theabove-mentioned scheme, and the proposed scheme may be transmitted by acombination scheme.

Detailed information contained in the CP zone information willhereinafter be described in detail.

Information (Parameter, Information) Transmitted for CP ZoneConfiguration

The CP zone proposed by the present invention may be defined as at leastone CP zone according to the purpose (for example, CP zone for randomaccess procedure or CP zone for BSR). That is, at least one of theplurality of CP zones may be configured for the same procedure. The atleast one CP zone is configured for the same procedure, informationregarding the at least one CP zone may be defined as informationregarding a single CP zone. In the meantime, the CP zone information mayinclude at least one of the following information 1) or 2).

1) UL Resource Information in which CP Zone is Configured

Information regarding the CP zone contained in SIB and MIB may includeUL resource information in which the CP zone is configured. For example,UL resource information may include information regarding the number (N)of CPRBs capable of being occupied by a plurality of UEs in the singleCP zone, as shown in FIG. 10. In addition, the UL resource informationmay include information regarding the number (M) of CP zones that may bedesired by one arbitrary UE attempting to occupy resources at a specifictime. As described above, (N×M) may indicate the number of candidateCPRBs, each of which can be selected by one arbitrary UE at a specifictime. That is, the UE may include (N×M) candidate CPRBs. In themeantime, the eNB may not configure the corresponding zone in all ULsubframes in consideration of resource usages.

2) Information Requisite for Transmission of Data Capable of beingTransmitted to the Configured CPRB

CP zone information contained in SIB and MIB may include informationneeded for transmission of data capable of being applied to theconfigured CPRB. Information needed for data transmission may includeinformation transmitted through the legacy UL grant.

At least one of a maximum RB (resource block) size, MCS (Modulation andCoding Scheme) level, an initial transmission power reference per UE maybe defined as information needed for transmission of data capable ofbeing applied to the configured CPRB. In the meantime, informationneeded for data transmission may be configured for all UEs accessing thecell.

Method for Configuring CP Zone

The method for configuring the CP zone will hereinafter be described onthe assumption of the random access procedure. In the random accessprocedure for use in the case in which the CP zone is not configured,the RRC message can be transmitted only in the case in which the ULgrant is received through a response message after PRACH transmission.On the other hand, if the random access procedure is performed throughthe CP zone, the UE may transmit the RRC message using the same time asin the preamble sequence or using the successive time resources. Thatis, if the CP zone is configured for the random access procedure, thePRACH and RRC messages may be transmitted using the same TTI (TransmitTime Interval), a neighbor TTI, other TTIs, etc. The relationshipbetween PRACH and the CP zone will hereinafter be described.

Referring to FIG. 11, a detailed method for configuring the CP zone forthe random access procedure according to one embodiment will hereinafterbe described. FIG. 11(a) shows the intra subframe configuration scheme,FIG. 11(b) shows the inter subframe configuration scheme, and FIG. 11(c)shows the mixed scheme of FIG. 11(a) and FIG. 11(b).

The PRACH and the CP zone may be configured using the intra subframeconfiguration scheme and the inter subframe configuration scheme.Alternatively, two schemes may be mixedly configured.

Referring to FIG. 11(a), the PRACH and the CP zone may be configuredaccording to the intra subframe configuration scheme. According to thisintra subframe configuration scheme, the PRACH and the RRC message maybe transmitted in the same subframe. In this case, the TDM (TimeDivision Multiplex) scheme or the FDM (Frequency Division Multiplex)scheme may be used. In this case, the RRC message may also betransmitted in the subframe used for PRACH transmission. This means thatthe RRC message is transmitted in a single TTI.

Referring to FIG. 11(b), the PRACH and the CP zone may be configuredaccording to the inter subframe configuration scheme. In accordance withthe inter subframe configuration scheme, the PRACH and the RRC messagemay be transmitted at different contiguous subframes. After the preambleis transmitted through one subframe, the RRC message may be transmittedin a subsequent subframe. That is, the PRACH and the RRC message may betransmitted at two TTIs.

In addition, the PRACH and the CP zone resources may be configured bymixing the above two schemes as shown in FIG. 11(c). For example,although PRACH is differently configured per subframe, the CP zone maybe configured at intervals of two subframes.

The PRACH and the CP zone may be configured in various schemes accordingto the cell management scheme. In the meantime, the PRACH or the CP zonemay not be configured in a specific subframe so as to maximally useresources contained in the cell. Through the definition of theabove-mentioned CP zone and the method for configuring the CP zone inthe cell, the latency time of the system can be minimized.

The random access procedure on the assumption that the CP zone isconfigured for the random access procedure will hereinafter be describedin detail.

FIG. 12 is a flowchart illustrating a random access procedure when theCP zone is not configured according to an embodiment. FIG. 13 is aflowchart illustrating a random access procedure when the CP zone isconfigured according to another embodiment.

Preamble transmission may be omitted according to the random accessprocedure as necessary. If the preamble transmission is omitted, the UEmay previously acquire the TA (Timing Alignment) value forsynchronization upon receiving DL data. In addition, the UE may notreceive the TA or may adjust the timing point using a timing differencein GPS or eNB without using the TA value as necessary. The followingdescription will disclose the random access procedure for use in thecase in which the preamble is transmitted to perform precise timingadjustment between the eNB and the UE.

FIG. 12(a) shows the contention-based random access procedure for use inthe case in which the CP zone is not configured. Referring to FIG.12(a), during the contention-based random access procedure, the UL grantfor the next UL message through the random access response message istransmitted from the eNB. If the CP zone is configured for the randomaccess procedure, the CP zone may be sued for the third transmission RRCmessage (e.g., RRC request message, NAS request message, etc.).

FIG. 13(a) shows the contention-based random access procedure for use inthe case in the CP zone is configured.

Referring to FIG. 13 (a), when the UE performs the random accessprocedure, the UE transmits the preamble and simultaneously orsuccessively transmits the RRC message. In more detail, the UE maytransmit the preamble, or at the same time or successively, may transmitthe RRC message without the UL grant through CPRB of a PUSCH selectedthrough contention. That is, the UE may perform a two-stage randomaccess procedure. That is, during the contention-based random accessprocedure, the UE may simultaneously or successively transmit a thirdmessage and the preamble of FIG. 11(a) using the CP zone.

FIG. 12(b) exemplarily shows the dedicated random access procedure foruse in the case in which the CP zone is not configured.

Referring to FIG. 12(b), the dedicated random access procedure mayinclude three-stage procedures through which the random access responsemessage is transmitted. During the dedicated random access procedure,the UL grant for the UL message that is transmitted through the randomaccess response message after completion of the random access procedureis transmitted from the eNB. If the CP zone is configured for thededicated random access procedure, the CP zone may be used to transmitthe RRC message transmitted after completion of the random accessprocedure.

FIG. 13(b) exemplarily shows the dedicated random access procedure foruse in the case in which the CP zone is configured.

Referring to FIG. 13(b), in the case of the noncontention-based randomaccess procedure, the UE may transmit the RRC message that can betransmitted after completion of the random access procedure during therandom access procedure. As a result, all the RRC procedures (forexample, handover execution) may be performed at a higher speed. In moredetail, the UE may transmit the preamble, or at the same orsuccessively, may transmit the RRC message without the UL grant throughCPRB of a PUSCH selected through contention. For example, if the UEperforms handover, the serving eNB may allocated the preamble to the UE.Thereafter, the eNB may transmit the preamble to the target eNB. If theCP zone is configured, the UE may transmit the preamble to the targeteNB using the CP zone, or may successively transmit the handover (HO)complete message to the target eNB.

The RRC message may be one of the following messages 1) to 3) accordingto the random access execution procedure. In the case of the initialaccess procedure (1), the RRC message may be the RRC connection requestmessage. In the case of the HO procedure (2), the RRC message may be theRRC connection reconfiguration complete message. In the case of the RRCconnection reconfiguration procedure, the RRC message may be the RRCconnection re-establishment request message.

The effects achieved when the CP zone for the random access procedure isconfigured will hereinafter be described with reference to FIGS. 8 and14.

FIG. 14 is a flowchart illustrating the effect achieved when the CP zonefor the random access procedure is configured. The contention-basedrandom access procedure will hereinafter be described with reference toFIG. 14(a), and the dedicated random access procedure will hereinafterbe described with reference to FIG. 14(b).

The effects achieved when the CP zone is configured for the randomaccess procedure are compared with those of FIG. 8, and the result ofcomparison will be given below.

Referring to FIG. 8(a), if the CP zone is not configured, the UEconfigured to perform the contention-based random access proceduretransmits the RACH preamble, receives the random access response fromthe eNB, and transmits the RRC/NAS request to the eNB. In this case, thestandard documents have disclosed a detailed description of the latencytime as shown in the above Table 1.

Referring to Table 1, a total latency time to the 8^(th) step in whichthe RRC connection configuration message is received (Component 8) shownin FIG. 8(a) is about 15.5 [ms].

Referring to FIG. 14(a), if the CP zone is configured, the UE does notreceive the random access response, and transmits the RRC/NAS requestmessage to the eNB simultaneously with or successively with transmissionof the RACH preamble. In this case, a latency time needed for receptionof the RRC connection configuration message is shown in the followingTable 3.

TABLE 3 Com- Time ponent 

Description 

(ms) 

1 

Average delay due to RACH scheduling 0.5 

period (1 ms RACH cycle) 

2-3 

RACH Preamble and Transmission of 1 

RRC and NAS Request 

4 

Preamble detection and Processing 4 

delay in eNB (L2 and RRC) 

5 

Transmission of RRC Connection 1 

Set-up (and UL grant) 

Referring to Table 3, a total latency time reaching the RRC connectionconfiguration message reception (component 8) corresponding to the5^(th) step of FIG. 14(a) is about 6.5 [ms]. That is, according to theCP zone configuration result, the latency time of about 9 [ms] may bereduced as compared to a previous latency time obtained before the CPzone configuration.

The following dedicated random access procedure will hereinafter bedescribed on the assumption of the HO procedure execution.

Referring to FIG. 8(b), the UE configured to perform handover (HO) fromamong the dedicated random access procedure for use in the case in whichthe CP zone is not configured may transmit the RACH preamble, receivethe random access response from the eNB, and transmit the RRC connectionreconfiguration complete message to the eNB. In this case, the standarddocuments have disclosed a detailed description of the latency time asshown in the above Table 2.

Referring to Table 2, a total latency time reaching DL data transmission(component 7) corresponding to the 7^(th) step of FIG. 8(b) is about10.5 [ms].

Referring to FIG. 14(b), if the CP zone is configured, the UE does notreceive the random access response, or simultaneously with orsuccessively with reception of the RACH preamble, may transmit the RRCconnection reconfiguration complete message to the eNB. In this case, alatency time needed for reception of the RRC connection configurationmessage is shown in the following Table 4.

TABLE 4 Com- Time ponent 

Description 

[ms] 

1 

Radio Synchronisation to the target cell 

1 

2 

Average delay due to RACH scheduling 0.5 

period (1 ms periodicity) 

3-4 

Transmission of RACH Preamble and UL data 

1 

5 

Preamble detection and Processing 4 

delay in eNB (L2 and RRC) 

6 

Transmission of RA response 

1 

Total delay 

7.5 

Referring to Table 4, a total latency time reaching the random accessresponse transmission corresponding to the 6^(th) step of FIG. 14(b) isabout 7.5 [ms]. That is, according to the CP zone configuration result,the latency time of about 3 ms may be reduced as compared to theprevious latency time achieved before the CP zone configuration. Thatis, the noncontention-based random access procedure for use in the casein which the CP zone is not configured must receive the UL grant messagefor RRC message transmission. However, if the CP zone is configured, thenoncontention-based random access procedure need not receive the ULgrant message, resulting in reduction of a latency time of a totalprocedure.

As described above, if the CP zone is configured for the random accessprocedure, the latency time caused by transmission/reception of the ULgrant message needed for RRC message transmission may be reduced.

However, since the UEs configured to perform random access occupies theresources through contention, collision may occur in the process foroccupying the corresponding resources.

FIG. 15 is a conceptual diagram illustrating a specific situation inwhich two UEs perform the random access procedure when the CP zone isconfigured.

FIG. 15 exemplarily shows one case in which two UEs successfully occupythe uplink (UL) CPRB and the other case in which two UEs fail to occupythe UL CPRB.

Referring to FIG. 15, the PRACH and the CP zone are configured accordingto the inter subframe scheme, so that the PRACH and the RRC message aretransmitted at different contiguous subframes. In addition, the CP zonedefined as one subframe may include two CPRBs (CPRB#1, CPRB#2). Asdescribed above, if UE 1 and UE 2 perform the random access procedure inthe cell in which two CPRBs are contained in one CP zone, UE 1 and UE 2may transmit the preamble through the same preamble sequence ordifferent preamble sequences. Respective UEs may transmit the preambleand at the same time may transmit the RRC message by occupying CPRB ofthe CP zone. In this case, UE 1 and UE 2 select the same CPRB (forexample, CPRB #2) through contention, collision occurs so that UE 1 andUE 2 may fail to occupy the CPRB.

In the meantime, if UE 1 and UE 2 occupy different CPRBs, UE 1 and UE 2may transmit the RRC message by successfully occupying resources. Aplurality of UEs may simultaneously transmit the same preamble sequence,so that the contention resolution process is needed.

As described above, although two or more UEs select different preamblesequences, if the two or more UEs attempt to occupy the CPRB in the sameCP zone, the random access procedure may fail due to the occurrence ofcollision. In addition, as the number of UEs configured tosimultaneously transmit data or to perform the random access procedureis increased, there is a higher possibility of causing PUSCH resourcecollision between UEs during the CPRB occupying process.

A method for minimizing the number of collisions generated in theresource occupying process when the CP zone is configured willhereinafter be described in detail.

FIG. 16 is a conceptual diagram illustrating a method for occupyingresources according to an embodiment of the present invention.

A method for occupying the CPRB by the UE configured to perform back-offwill hereinafter be described with reference to FIG. 16.

If the UE transmits a PRACH, the UE may arbitrarily select the CPRBwithin the CP zone, and may transmit the RRC message. If UE 1 and UE 2select the same CPRB, each UE may perform back-off. Each of UE 1 and UE2 may select the CPRB within the CP zone after lapse of each back-offtime, and may transmit the RRC message.

If UE 1 and UE 2 do not transmit the PRACH, for example, if the UEcalculates a TA without transmitting the preamble using a GPS (GlobalPositioning System) through a time difference with a neighbor eNB, eachUE may arbitrarily select the CPRB in the CP zone at a specific time atwhich the random access procedure is performed, and may transmit the RRCmessage. Alternatively, each UE configured to use the back-off time mayselect the CPRB in the CP zone after lapse of a back-off time, and maytransmit the RRC message.

Assuming that UE 1 is located far from UE 2, although the eNB maysuccessfully receive the RRC message when the random access procedure isperformed using the same resources, the eNB may successfully receive theRRC message. Assuming that UE 1 and UE 2 are located very close to eachother, when collision occurs, the eNB may have difficulty insuccessfully receiving data. Accordingly, the above-mentioned method isbeneficial to a method for occupying resources between neighboring UEs.

FIG. 17 is a conceptual diagram illustrating a method for occupyingresources according to another embodiment of the present invention.

Referring to FIG. 17, a method for minimizing the number of collisiontimes generated in the resource occupying process when the CP zone isconfigured will hereinafter be described. FIG. 17(a) shows the TDMscheme based on the resource division scheme, and FIG. 17(b) shows theFDM scheme based on the resource allocation division scheme. Each UE mayselect the CPRB as a preamble sequence. In this case, the preamblesequence may be arbitrarily selected by the UE, or may be a sequenceallocated from the eNB. In this case, the relationship between theUE-selected CPRB and the preamble sequence is shown in the followingequation 1.(Number of UE-selected CPRB block)=(Selected Preamble Sequence)modN  [Equation 1]

The number of the UE-selected CPRB block is obtained when the modulooperation is performed using the selected preamble sequence (N). Thatis, the CPRB block selected by the UE may correspond to a remaindervalue obtained when the selected preamble sequence is divided by N. Inthis case, N may indicate the number of CPRB blocks capable of beingoccupied by the UE configured to transmit the preamble. The UE mayobtain the N value through system information.

FIG. 17 assumes that N is set to 4. Referring to FIG. 17(a), if UE 1receives the preamble sequence #2 from the eNB and selects the preamblesequence #2, the number of a UE-selected CPRB block is denoted by ‘2 mod4=2’. Meanwhile, if UE 2 selects the preamble sequence #4, the number ofa UE-selected CPRB block is denoted by ‘4 mod 4=0’.

The above-mentioned CPRB block selection scheme may also be applied tothe FDM scheme. Referring to FIG. 17(b), if UE 1 receives and selectsthe preamble sequence #2 from the eNB, The number of a UE-selected CPRBblock is denoted by ‘2 mod 4=2’. In the meantime, if UE 2 selects thepreamble sequence #4, the number of a UE-selected CPRB block is denotedby ‘4 mod 4=0’.

On the other hand, in the contention-based random access procedure, oneor more UEs may simultaneously select the same CPRB in the same CP zone,resulting in the occurrence of a data transmission failure. If the sameCPRB is selected so that a transmission failure occurs, the eNB maycommand the UE to perform the four-stage random access procedure towhich the CP zone is not applied.

During the dedicated random access procedure, the CPRB is occupied basedon the pre-allocated preamble sequence. Therefore, it is necessary forthe eNB to allocate the preamble sequence in such a manner that acollision in the PUSCH occupying process between UEs configured toperform the dedicated random access procedure is prevented fromoccurring.

FIG. 18 is a flowchart illustrating a random access procedure performedbased on the resource occupying method shown in FIG. 17. FIG. 18(a)shows the contention-based random access procedure, and FIG. 18(b) showsthe dedicated random access procedure.

Referring to FIG. 18(a), UE 1 and UE 1 may directly select the preamblesequence, and transmit the selected preamble sequence as describedabove. Accordingly, the same CPRB may be selected for transmission ofthe RRC message. In this case, the eNB may recognize the occurrence of acollision in CPRB, and may transmit the RA-RNTI decided by the preambleto each UE, so that the eNB may indicate the execution of four-stagerandom access procedure. In this case, the RA-RATI transmitted to eachUE may be different RA-RNTIs. As can be seen from FIG. 18, RA-RNTIapplied to UE 1 is denoted by ‘RA-RNTI y’, and RA-RNTI applied to UE 2is denoted by ‘RA-RNTI x’. UE 1 and UE 2 may transmit the RRC connectionrequest message to the eNB upon receiving an indication message from theeNB, and may receive the RRC connection configuration message from theeNB.

During the dedicated random access procedure, the eNB may allocate thepreamble sequence. Referring to FIG. 18(b), the eNB may allocate thepreamble sequence x to the UE 1, and may allocate the preamble sequencey to the UE 2. In this case, the eNB may determine the preamble sequencex and the preamble sequence y in such a manner that there is no CPRBcollision between the CPRB-selected UEs. UE 1 and UE 2 may decide thepreamble sequence allocated from the eNB and may decide the CPRB basedon Equation 1, so that the UE 1 and the UE 2 may transmit the RRCconnection request message without collision.

FIG. 19 is a flowchart illustrating a resource occupying methodaccording another embodiment of the present invention.

FIG. 19(a) exemplarily shows one case in which two UEs simultaneouslyoccupy the CPRB, and FIG. 19(b) exemplarily shows the other case inwhich three UEs simultaneously occupy the CPRB.

Each UE may select the CPRB based on a preamble sequence. In this case,it is assumed that FDR (Full Duplex Relay) is applied to the UE.Therefore, the corresponding UE may transmit the preamble sequence, andmay receive the preamble of a neighbor UE configured to transmit therandom access preamble. In this case, since the corresponding UE canobtain the preamble sequence selected by a neighbor UE, the CPRB isselected to prevent the occurrence of a collision according to thefollowing rules, so that the RRC request message may be transmitted.

According to the description of FIG. 17, if 2 CPRBs are present in theCP zone (i.e., N=2), and if UE 1 selects the preamble sequence 2, thenumber of a CPRB block is denoted by ‘2 mod 2=0’. If UE 2 selects thepreamble sequence 4, the number of a CPRB block is denoted by ‘4 mod2=0’. Therefore, UE 1 and UE 2 may attempt to occupy the CPRB block #0,so that a collision may occur.

On the other hand, according to the description of FIG. 19, a specificUE recognizes which preamble number is selected by a neighbor UE. If thesame CPRB is selected, CPRB may be allocated to preamble sequences ofthe UEs configured to simultaneously transmit data in descendingnumerical order or in ascending numerical order.

In more detail, as can be seen from FIG. 19(a), it can be recognizedthat UE 1 selects the preamble sequence #2 and UE 2 selects the preamblesequence #4. In this case, the preamble sequence selected by UE 1 is ata lower number, CPRB #0 is occupied. In this case, it is assumed thatresource allocation is performed in ascending numerical order of thepreamble sequence.

UE 2 recognizes that UE 1 has selected the preamble sequence #2. Thepreamble sequence selected by UE 2 is at a higher number, CPRB #1 isoccupied, so that UE 2 may transmit the RRC message to the eNB throughCPRB #1.

In the meantime, as can be seen from FIG. 19(b), UE 1, UE 2, and UE 3respectively select a preamble sequence 2, a preamble sequence 4, and apreamble sequence 8, so that they can select the same CPRB usingEquation 1. However, respective UEs can obtain the preamble sequenceinformation of a neighbor UE, such that UEs arranged in ascendingnumerical order of the preamble sequence can sequentially select lowerCPRBs. In this case, since the number of CPRBs is less than the numberof UEs, UE 3 having the highest preamble sequence value may discard RRCmessage transmission. Alternatively, UE 3 may attempt to retransmitafter lapse of a predetermined back-off time.

The above-mentioned method is designed to sequentially allocate theCPRBs in ascending numerical order of the preamble sequence. Therefore,a UE having selected a lower preamble sequence always has priority.However, the CPRB selection method is not limited thereto, and the CPRBselection rule combined in various orders may also be applied to theCPRB selection method as necessary.

A method for occupying resources based on a UE ID according to anotherembodiment of the present invention will hereinafter be described indetail.

Each UE may select the CPRB based on a UE ID. In this case, therelationship between the UE-selected CPRB and the UE ID is denoted bythe following equation 2.(Number of UE-selected CPRB block)=(UE ID)mod N  [Equation 2]

A number of the UE-selected CPRB block is obtained when an ID of theselected UE is modulo-operated by N. That is, the UE-selected CPRB blockmay correspond to a remainder value obtained when a UE ID is divided byN, where N is the number of CPRB blocks capable of being occupied by aUE configured to perform the random access procedure. This N value maybe obtained through the system information. In this case, a UE ID is aparameter capable of identifying a subscriber, and may be a singleuniversal UE ID. For example, the UE ID may be an International MobileSubscriber Identity (IMS), a Globally Unique Temporary Identifier(GUTI), an SAE Temporary Mobile Subscriber Identity (S-TMSI), an IPaddress (PDN (Packet Data Network) address), etc. Alternatively, forexample, a parameter used to identify each UE for use in the cell may bea C-RNTI. That is, this parameter can be applied to a UE ID that is usedin the cellular network in various ways.

A method for selecting the CPRB based on the UE ID can be applied to therandom access procedure in which no preamble is transmitted, and canalso be applied to select the CPRB in the other procedure but not therandom access procedure.

In the meantime, during the contention-based random access procedure,one or more UEs can simultaneously select the same CPRB for use in thesame CP zone. In this case, data transmission failure may occur. If thesame CPRB is selected and unexpected collision occurs, the eNB maycommand the UE to perform the four-stage random access procedure towhich the CP zone is not applied.

As described above, according to the CPRB selection method proposed bythe present invention, there is a lower probability of causing collisionwhen one or more UEs simultaneously occupy the CPRB, so that the dataTx/Rx procedure can be quickly performed.

In addition, although two or more UEs select different preamblesequences, the data Tx/Rx failure may occur due to the occurrence of acollision in the resource occupying process when the same CP zone isused. However, according to the CPRB selection method proposed by thepresent invention, in the case in which a resource collision between UEsconfigured to transmit different preamble sequences occurs, the eNBhaving recognized the above-mentioned case converts the random accessprocedure of the UE into four stages, so that unnecessary random accessprocedures caused by the resource collision can be prevented fromoccurring.

FIG. 20 is a block diagram for an example of a communication deviceaccording to one embodiment of the present invention.

Referring to FIG. 20, a wireless communication system includes a BS 110and a UE 120. When the wireless communication system includes a relay,the BS or UE can be replaced by the relay.

For downlink, transmitter may be part of the BS 110, and receiver may bepart of the UE 120. For uplink, transmitter may be part of the UE 120,and receiver may be part of the BS 110.

The BS 110 includes a processor 112, a memory 114 and a radio frequency(RF) unit 116. The processor 112 may be configured to implement theprocedures and/or methods proposed by the present invention. The memory114 is connected to the processor 112 and stores information related tooperations of the processor 112. The RF unit 116 is connected to theprocessor 112 and transmits and/or receives an RF signal. The UE 120includes a processor 122, a memory 124 and an RF unit 126. The processor122 may be configured to implement the procedures and/or methodsproposed by the present invention. The memory 124 is connected to theprocessor 122 and stores information related to operations of theprocessor 122. The RF unit 126 is connected to the processor 122 andtransmits and/or receives an RF signal. The BS 110 and/or the UE 120 mayinclude a single antenna or multiple antennas.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present invention, a description is madecentering on a data transmission and reception relationship among a BSand a UE. In some cases, a specific operation described as performed bythe BS may be performed by an upper node of the BS. Namely, it isapparent that, in a network comprised of a plurality of network nodesincluding a BS, various operations performed for communication with anMS may be performed by the BS, or network nodes other than the BS. Theterm ‘BS’ may be replaced with the term ‘fixed station’, ‘Node B’,‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The term ‘UE’may be replaced with the term ‘Mobile Station (MS)’, ‘Mobile SubscriberStation (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means. The BS 110 includes aprocessor 112, a memory 114 and a radio frequency (RF) unit 116. Theprocessor 112 may be configured to implement the procedures and/ormethods proposed by the present invention. The memory 114 is connectedto the processor 112 and stores information related to operations of theprocessor 112. The RF unit 116 is connected to the processor 112 andtransmits and/or receives an RF signal. The UE 120 includes a processor122, a memory 124 and an RF unit 126. The processor 122 may beconfigured to implement the procedures and/or methods proposed by thepresent invention. The memory 124 is connected to the processor 122 andstores information related to operations of the processor 122. The RFunit 126 is connected to the processor 122 and transmits and/or receivesan RF signal. The BS 110 and/or the UE 120 may include a single antennaor multiple antennas.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a UE, BS or other apparatuses ofa wireless communication apparatus.

The invention claimed is:
 1. A method for transmitting data to a basestation (BS) by a first user equipment (UE), the method comprising:receiving, from the BS, information on a contention-based physicaluplink shared channel (PUSCH) zone including a plurality ofcontention-based PUSCH resource blocks; receiving, from a second UE, apreamble sequence of the second UE; determining at least onecontention-based PUSCH resource block from the contention-based PUSCHzone based on the preamble sequence of the second UE; and transmitting,to the BS, the data using the at least one contention-based PUSCHresource block.
 2. The method according to claim 1, wherein the at leastone contention-based PUSCH resource block is determined by the followingequation,Contention-based PUSCH resource block=(preamble sequence)modN  [Equation] wherein mod is a modulo operation, and N is a number ofcontention-based PUSCH resource blocks contained in the contention-basedPUSCH zone, and wherein the preamble sequence is the preamble sequenceof the second UE or a preamble sequence of the first UE.
 3. The methodaccording to claim 1, wherein the at least one contention-based PUSCHresource block is sequentially determined with respect to the preamblesequence of the second UE.
 4. The method according to claim 1, whereinthe preamble sequence of the second UE is for a random access procedure.5. A method for receiving data by a base station (BS), the methodcomprising: transmitting, to a first user equipment (UE), information ona contention-based physical uplink shared channel (PUSCH) zone includinga plurality of contention-based PUSCH resource blocks; and receiving,from the first UE, the data using at least one contention-based PUSCHresource block wherein the at least one contention-based PUSCH resourceblock is determined based on the preamble sequence of a second UE fromthe contention-based PUSCH zone.
 6. The method according to claim 5,wherein the at least one contention-based PUSCH resource block isdetermined by the following equation,Contention-based PUSCH resource block=(preamble sequence)modN  [Equation] wherein mod is a modulo operation, and N is a number ofcontention-based PUSCH resource blocks contained in the contention-basedPUSCH zone, and wherein the preamble sequence is the preamble sequenceof the second UE or a preamble sequence of the first UE.
 7. The methodaccording to claim 6, further comprising: allocating the preamblesequence of the first UE and the preamble sequence of the second UE,wherein the preamble sequence of the first UE and the preamble sequenceof the second UE are determined as a different contention-based PUSCHresource blocks based on the equation.